With lower level properties, I think rental and financial conditions have actually created a situation where only people willing to be slumlords can make it financially viable.
I used to feel a bit differently about this, but I've since had the experience of being a landlord for a short time, where we very quickly lost money because the tenant simply didn't pay. It took months to get her out, and had we been paying a mortgage on the place we'd have been hosed. As it was, we lost quite a bit on utilities. I'd never do it again, had this tenant damaged the property we would have been ruined financially, and this was a property that we essentially inherited, so no real capital investment. It's just too risky.
I've also worked more recently in a job where I am dealing a lot with people living in the very bottom tier of housing, or who are unhoused and that is the kind of housing they are trying to get into. There is a significant percentage of those people who are never going to reliably pay rent, but even if the state pays for them, they will destroy the property. One of my good friends was miserable for half a year because a person like this moved in across the hall, and quickly filled the tiny room with trash, and a cat, and the stench went throughout the whole house, to the point that the guy living downstairs moved out. They still haven't been able to rent the flat because the smell is under the floorboards, and I imagine in the end they will have to replace the flooring. This is after they renovated the flat after the last tenant left.
The only way they can make money off of these properties is to put nothing into them that isn't absolutely required/drug out of them, and hope the value of the land and property simply rises with inflation.
The "nice" inexpensive flats never rent to anyone questionable, they are looking for seniors often, with references, and ideally recommended personally by other good tenants. But there aren't enough even for everyone who would be a good tenant.